1. Field of the Invention
The invention relates to a vehicle side airbag device that restrains a seated occupant by a side airbag in the event of a side collision of a vehicle.
2. Description of Related Art
A side airbag device described in International Publication No. WO 2010/076881 includes a left-right two-chamber side airbag. This side airbag has a third base fabric sandwiched between a first base fabric on an occupant side and a second base fabric on a door side, such that a first bag half on the occupant side and a second bag half on the door side are formed. Gas from an inflator is supplied to this second bag half, and gas is supplied to the first bag half via a communication hole formed in an end portion, on a side away from the inflator, of the third base fabric. As a result, first the second bag half is inflated and deployed to ensure the minimum required occupant restraint performance, and then the first bag half is deployed. That is, when the second bag half inflates and deploys, it (i.e., the second bag half) is able to deploy smoothly without interfering with the occupant, by a thickness of the second bag half in a vehicle width direction being set small. Then sufficient thickness in the vehicle width direction of the entire side airbag is ensured by completing the inflation and deployment of the first bag half, thereby increasing the occupant restraint performance.
Meanwhile, with a side airbag device described in Japanese Patent Application Publication No. 2011-051414 (JP 2011-051414 A), a side airbag is a left-right independent two-chamber side airbag that is provided with a small first airbag that inflates and deploys between a shoulder of an occupant and a side door, and a large airbag that is sewn to the side door-side of the first airbag. The first airbag finishes inflating and deploying before the second airbag does, and a horizontal cross-section after inflation and deployment is formed in a tapered shape on a front side. As a result, even if a space between the occupant and the side door is narrow in a compact vehicle or the like, the side airbag will inflate and deploy stably by first inflating and deploying the first airbag in the space, and then inflating and deploying the second airbag.
However, with each of the side airbag devices described in the publications described above, the structure of the airbag is complex. Therefore, many base fabrics are required, and the sewing work is complicated, which leads to an increase in the manufacturing cost. Moreover, when folded, the side airbag is bulky and may not be able to be housed in a compact vehicle seat.